[MergeFuncs] Call removeUsers() prior to unnamed_addr RAUW

[nikic]

Summary

For unnamed_addr functions we RAUW instead of only replacing direct callers. However, functions in which replacements were performed currently are not added back to the worklist, resulting in missed merging opportunities.

Fix this by calling removeUsers() prior to RAUW.

[nikic]

Remove some trailing semicolons in the test file ... hard to break that habit.

[whitequark]

LGTM, thanks for fixing this!

[nikic]

@whitequark I don't have commit access, could I ask you to land this patch?

lib/Transforms/IPO/MergeFunctions.cpp

if (F->isInterposable()) {
     // call sites to point to F even when within the same translation unit.
     if (!G->isInterposable() && !MergeFunctionsPDI) {
       if (G->hasGlobalUnnamedAddr()) {
         // G might have been a key in our GlobalNumberState, and it's illegal
         // to replace a key in ValueMap<GlobalValue *> with a non-global.
         GlobalNumbers.erase(G);
         // If G's address is not significant, replace it entirely.
         Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
+        removeUsers(G);
         G->replaceAllUsesWith(BitcastF);
       } else {
         // Redirect direct callers of G to F. (See note on MergeFunctionsPDI
         // above).
         replaceDirectCallers(G, F);
       }
     }
 

test/Transforms/MergeFunc/unnamed-addr-reprocessing.ll

+; RUN: opt -S -mergefunc < %s | FileCheck %s
+
+; After test3 and test4 have been merged, we should detect that
+; test1 and test2 can also be merged.
+
+; CHECK: define void @test4() unnamed_addr
+; CHECK-NEXT: tail call void @test3()
+; CHECK: define void @test2() unnamed_addr
+; CHECK-NEXT: tail call void @test1()
+
+declare void @dummy()
+  
+define void @test1() unnamed_addr {
+    call void @test3()
+    call void @test3()
+    ret void
+}
+
+define void @test2() unnamed_addr {
+    call void @test4()
+    call void @test4()
+    ret void
+}
+
+define void @test3() unnamed_addr {
+    call void @dummy()
+    call void @dummy()
+    ret void
+}
+
+define void @test4() unnamed_addr {
+    call void @dummy()
+    call void @dummy()
+    ret void
+}